Method of increasing catalyst activity in sour crude catalytic reformers

ABSTRACT

A method of operating at least two catalytic reformers which produce recycle streams of different sulfur content in which a portion of the lower sulfur content stream is recycled to the unit producing the higher sulfur content recycle steam to reduce the sulfur content of the stream recycled to the latter reformer.

United States Patent Roark 51 June 13, 1972 [54] METHOD OF INCREASING CATALYST 3,067,130 12/1962 Baldwin et a1. ..208/140 ACTIVITY IN SOUR CRUDE 3,328,476 6/1967 Cabbage ..260/667 CATALYTIC REFORMERS 3,306,841 2/1967 Ward ..208/134 X 3.516924 6/1970 Forbes ..208/65 [72] Inventor: WIIIIam G. Roark, Sweeny, Tex. 2,931,768 4/1960 Mathy et al... 208/79 2 937 134 5/1960 Bowles t. ....208/89 73 A Ph 11 I 1 ssgnee pe'mlwm Gummy 3,000,810 9/1961 Christensen et a1. ..208/79 [22] Filed: Oct. 19, 1970 Primary Examiner-Delbert E. Gantz [2 1] Appl' SL833 Assistant Examiner-G. E. Schmitkons AuomeyYoung & Quigg [52] US. Cl ..208/79, 208/134, 208/141,

208/209 [57] ABSTRACT 51 I t. I. E g Search A method of operating at least two catalyttc reformers whlch 208/209 produce recycle streams of different sulfur content in which a portion of the lower sulfur content stream is recycled to the 56 unit producing the higher sulfur content recycle steam to I 1 References Cited reduce the sulfur content of the stream recycled to the latter UNITED STATES PATENTS l'eformer' 3,01 1,967 12/1961 Schmltkons et a1 ..208/139 5 Claims, 1 Drawing Figure PATENTEDJuu 13 I972 INVENTOR.

W. G. ROARK ATTORNEYS METHOD OF INCREASING CATALYST ACTIVITY IN SOUR CRUDE CATALYTIC REFORMERS This invention pertains to catalytic reforming.

In one of its more specific aspects, this invention pertains to a method of increasing catalyst activity in sour crude catalytic reformers.

Catalytic reforming of petroleum-derived feedstocks is well known. In the conventional operation, various liquid products are recovered and there is produced an off-gas stream which is comprised principally of hydrogen. A portion of this stream, which can have a sulfur content almost directly related to the sulfur content of the feedstock, is recycled to the unit.

Frequently, two or more such reforming units are operated simultaneously and frequently on different feedstocks. Each will realize a different catalyst life, and the catalyst life which each realized will be inversely related to the sulfur content of the off-gas recycle stream.

There has now been discovered a method of improving operation, particularly to the catalyst life, of at least one of such a plurality of catalytic reformers to which are charged a plurality of different feedstocks having different sulfur content. This invention provides such a method.

According to this invention there is provided a method of increasing the catalyst life of at least one of a plurality of catalytic hydrocarbon reforming units to which are charged at least two feedstocks containing different sulfur quantities and which produce recycle streams of different sulfur contents. A portion of the lower sulfur-content recycle stream is introduced into the higher sulfur content recycle stream which is recycled to one of the units in a quantity sufficient to effectively lower the sulfur content of the recycle stream to that unit and to improve its catalyst life.

The method of this invention contemplates introducing a portion of that off-gas from the unit to which is charged the lower sulfur content feed into that stream of off-gas recycled to the unit to which is charged the higher sulfur-content feed. In effect, this procedure has the effect of shifting the equilibrium sulfur content on the catalyst by converting some of the sulfur accumulated on the catalyst to hydrogen sulfide. This reduction of sulfur content of the catalyst increases its activity and this increases its operating temperature. As a result, a further reduction of the sulfur content results and longer catalyst life is realized.

The amount of gas which is recycled from the unit charging the low sulfur charge stock to the unit charging the high sulfur charge stock should be as large as possible in order to obtain the maximum improvement. it may happen that the two units are of such relative sizes that the entire quantity of recirculated gas required by that unit charging the high sulfur charge stock can be obtained by supplying the off-gas from the unit charging the lower sulfur charge stock. In this instance, the maximum benefit is realized in practicing the method of this invention.

In any instance, the quantity of low sulfur-content recycle introduced into the high sulfur-content recycle should be sufficient to effectively lower the sulfur content of the later stream. In doing so, a portion ofthe high sulfur-content stream can be displaced so that the quantity of recycle is not in creased. This quantity will vary depending on the relative quantities of the recycle streams concerned and their sulfur contents.

The method of this invention will be more easily understood by referring to the attached drawing.

This drawing shows two individual cracking units 1 and 2 being charged with charge stocks through conduits 3 and 4, respectively.

Unit I is charged with a high sulfur content feed and produces, among other product streams, a C, and heavier cut through conduit 5 and a hydrogen off-gas stream having a relatively high sulfur content through conduit 6. Some portion of this off-gas hydrogen stream is recycled to unit 1 through conduit 7.

Unit 2 is charged with a low sulfur content feed and produces, among other product streams, a C. and heavier cut through conduit 8 and a hydrogen ofi-gas stream having a relatively low sulfur content through conduit 9. Some portion of this off-gas hydrogen stream is recycled to unit 2 through conduit l0.

Because the sulfur content of that stream produced through conduit 9 is less than that produced through conduit 6, after that quantity of off-gas required to be reintroduced into unit 2 through conduit 10 is satisfied, as large a quantity of this lower sulfur-content gas as possible is then introduced from conduit 9 through conduit 11 into unit 1. The amount of off-gas recycled to unit 1 from conduit 6 is reduced accordingly so that the sulfur content of those streams reintroduced into both units l and 2 is at a minimum. In this manner, the catalyst life of unit 1 is improved as are its yields.

The following example indicates one of the best modes of carrying out the invention and the decided advantages in doing so. Two methods of operation were carried out. In the Before operation, the method of this invention was not followed. In the "Invention" method, the recycle method from the one unit to the other was carried out.

During the period concerned, both units were employing a prereduced, presulfided platinum supported catalyst. No. 1 unit was processing a 60 AP] gravity l325 F. boiling range material having a relatively high sulfur content of 80-200 ppm to produce benzene and toluene. No. 2 was processing a 54 API gravity 240-400 F. boiling range material containing less than 5 ppm sulfur to produce motor fuel. Operating conditions and results before and after practicing the invention were as follows:

BEFORE Unit l Unit 2 Feed Rate, BPD l4,000 l4,000 S Content of Feed, ppm [60 5 C, Yield, 90 88 H, Recycle Yield, H, 88 88 H, Recycle S Content, wt. 0.04 0.005 Recycle to Unit, MSCFD 1 10,000 1 15,000 Catalyst Bed Temperature, F. 931 928 Catalyst Life, days 290 700 INVENTION Unit I Unit 2 Feed Rate, BPD 14,000 14,000 S Content of Feed 160 5 C, Yield, 96 89 88 H, Recycle Yield, H, 90 88 H Recycle S Content, wt. 0.03 0.005 Recycle to Unit, MSCFD ll(l,000 l l5,000 Recycle to Unit l, MSCFD ll,000 Catalyst Bed Temperature, T. 915 928 Catalyst Life, days 360 700 Percent Recycle Supplied to No. 1 Unit 90 l0 Percent 5 Reduction by Recycling 25 0 Summarily, the above data indicate that when no low sulfur hydrogen off-gas was recycled from No. 2 unit to No. 1 unit, the catalyst life of that catalyst employed in Unit No. l was 290 days as related to a recycle off-gas sulfur content of 0.04.

However, when low sulfur hydrogen off-gas was recycled from No. 2 unit to No. 1 unit and the total recycle off-gas sulfur content reduced to 0.03, the catalyst life of the catalyst of unit No. l was improved from 290 days to 360 days.

It will be evident from the foregoing that various modifications can be made to the method of this invention. Such, however, are considered as being within the scope of the invention.

What is claimed is:

l. A method of operating at least two catalytic reformers, the first of said reformers producing a low sulfur content recycle stream and the second of said reformers producing a high sulfur content recycle stream, said recycle streams being reintroduced into said reformers, which comprises introducing a portion of said low sulfur content recycle stream from said 4. The method as defined in claim 1 in which the quantity of recycle introduced into said second reformer from said first reformer is about 10 percent of the total quantity of recycle introduced into said second reformer.

5. The method as defined in claim 1 in which the quantity of recycle introduced into said second reformer is suflicient to reduce the sulfur content of said recycle stream to said second reformer by about 25 percent.

II l I 1 

2. The method as defined in claim 1 in which the quantity of recycle stream introduced into said second reformer from said first reformer is sufficient to increase the catalyst life of the catalyst of said second reformer.
 3. The method as defined in claim 1 in which the total quantity of recycle introduced into said second reformer is introduced from said first reformer.
 4. The method as defined in claim 1 in which the quantity of recycle introduced into said second reformer from said first reformer is about 10 percent of the total quantity of recycle introduced into said second reformer.
 5. The method as defined in claim 1 in which the quantity of recycle introduced into said second reformer is sufficient to reduce the sulfur content of said recycle stream to said second reformer by about 25 percent. 